Conversion and coking of hydrocarbon oils



March 2, 1937. E. F. NELSON 2,072,378

CONVERSION AND COKING OF HYDROCARBQN OILS 'Ffi.=led'March so, 1952RECEIVER FURNACE I NVENTOR EDWIN F. NELSON wazz ATTORN Patented Mar. 2,1937 UNITED STATES CONVERSION AND COKING OF HYDROCAR- BON OILS Edwin F.Nelson, Chicago, Ill., assignor, by mesne assignments, to Universal OilProducts Company, Chicago, 111., a corporation of Delaware ApplicationMarch 30,

3 Claims.

This invention relates to the conversion and coking of hydrocarbon oilsand more particularly refers to an improved process and apparatus forthe conversion of hydrocarbon oil and coking of 5 the residual oilproduced thereby, said coking being assisted by direct contact betweenthe residual oil and highly heated raw oil charging stock to be cracked.

In one of its specific embodiments, the inven- 110 tion comprises animprovement of the type of cracking operation wherein hydrocarbon oil issubjected to conversion in a'heating coil, the heated oil, is passedthrough an enlarged reaction zone maintained at superatmosphericpressure .15 wherein conversion, particularly of the vaporous products,may continue, vaporous and non-vaporous products are withdrawnsimultaneously from the reaction chamber and introduced into a reducedpressure vaporizing chamber, vapors from the vaporizing chamber aresubjected to fractionation, their heavier components, which arecondensed by fractionation, being returned to the heating coil forfurther conversion while the light vaporous overhead product iswithdrawn from the fractionator, subjected to condensation and theresulting distillate and gas collected, said improvement comprisingwithdrawing from said vaporizing chamber residual oil remainingunvaporized therein and introducing it into a coking zone, heating rawoil charging stock for the system to a high temperature and introducingit into direct contact with the residual oil in said coking zone, forthe purpose of supplying heat thereto and. assisting reduction of theresidual oil to coke, and returning vapors from said coking zone to saidreduced pressure vaporizing chamber.

The raw oil charging stock, prior to its introduction into the cokingzone, is heated to a temperature suificient to eiTect reduction of theresidual oil therein to coke. This temperature may be'of the order of900 to 950 F. or thereabouts but the time to which the raw oil issubjected to this high temperature is regulated, dependent upon the typeof raw oil charging stock utilized, so that no substantial formation anddeposition of coke occurs in the heating coil through which the raw oilcharging stock is passed. As time is one of the factors governing thedegree of conversion, it is possible to subject the raw oil chargingstock to very little or to extensive conversion, as desired, andparticularly with heavy charging stocks such as residual oils, fueloils.

L55 heavy crudes and the like, coking of some of the 1932, Serial No.602,014

heavier components of the raw oil may also be the cracking systemtogether with lighter relatively clean reflux condensate. This advantagewill be immediately recognized by those familiar with the cracking artand does not require extensive explanation. However, it permits, amongother things, the use of a wide variety of charging stocks without thenecessity of short operating periods, due to excessive deposition ofcoke in thecracking coil, and permits, even with relatively heavycharging stocks, the use of higher conversion temperatures than wouldotherwise be possible without excessive gas formation and coking in theheating coil. Also, when appreciable conversion of the raw oil isaccomplished by the treatment to which it is subjected in the cokingoperation, further conversion of the resulting intermediate conversionproducts, which is accomplished in the main cracking system, results inthe production of substantial yields of motor fuel high in anti-knockvalue.

One specific form of apparatus in which the process of the presentinvention may be practiced is illustrated in the attached diagrammaticdrawing. A heating coil l receives hydrocarbon oils to be cracked fromsources which will be later more fully described and, by means of heatsupplied from a furnace 2 of any suitable form, the oil is heated to thedesired conversion temperature and is discharged through line 3 andvalve 4 into reaction chamber 5. Chamber 5, like heating coil l, ispreierably maintained at substantial superatmospheric pressure and thevaporousproducts from the heating coil, which pass through the reactionzone at a slower rate than the heavier liquid conversion products, aresubjected to continued conversion in the reaction zone for a greaterlength of time than said heavier liquids. Both vaporous and non-vaporousconversion products are withdrawn from reaction chamber 5 through line Band valve 1 and are introduced into vaporizing chamber 8,

which is preferably maintained at substantially reduced pressurerelative to that employed in chamber 5.

Vaporous conversion products and residual liquid separate in chamber 8,the vapors pass through line 9 and Valve H] to fractionation infractionator II.

The relatively heavy components of the vapors are condensed in thefractionator and are withdrawn as reflux condensate from its lowerportion through line l2 and valve l3 to pump l4 which supplies this oilthrough line I5 and valve IE to heating coil I for conversion.

vaporous products remaining uncondensed in fractionator H are removedfrom its upper portion through line H and valve l8, are subjected tocondensation and cooling in condenser I9 and the resulting distillateand gas passes through line 20 and valve 2! to be collected in receiver22. Uncondensable gas may be released from the receiver through line 23controlled by valve 24. Distillate may be withdrawn from the receiverthrough line 25 and valve 26. A portion of the distillate from receiver22 may, when desired, be recirculated by means of line 21, valve 28,pump 29, line and valve 3| to the upper portion of fractionator H toassist fractionation in this zone and to control the vapor outlettemperature.

Residual oil remaining unvaporized in chamher 8 is withdrawn throughline 32 and valve 33 to pump 34 from which it is fed through line 35either into coking chamber 36 through line 3! and valve 38 or intocoking chamber 36' through line 31' and valve 38'. Coking chambers 36and 36 are alternate coking zones wherein the cracked residual oil isreduced to substantially dry carbonaceous residue. It is, of course,within the scope of the invention to employ a single coking chamber or,when desired, more than the two illustrated in the drawing. The objectof employing more than one coking zone is to permit one to be cleanedand prepared for operation while the other is being operated and thusprolong the operating cycle of the process. Raw oil charging stock forthe system supplied through line 39 and valve 40 to pump 4| is fedthrough line 42 and valve 43 to heating coil 44. The raw oil may, ofcourse, be preheated in any well known manner not illustrated in thedrawing, prior to its introduction into heating coil 44, for example, byindirect contact with relatively hot liquid and/or vaporous conversionproducts of the process. The raw oil is heated in heating coil 44, bymeans of heat supplied from a furnace 45 of any suitable form, to atemperature suificient to subsequently effect coking of the crackedresidual oil by direct contact therewith. The heated raw oil chargingstock is discharged from heating coil 44 through line '46 and may passto coking chamber 36, through valve 41 in this line, or into cokingchamber 36', through line 46' and valve 41'. Direct contact is obtainedin the coking zone between the highly heated raw oil charging stock andthe residual oil from vaporizing chamber 8 and the heat thus imparted tothe residual oil effects its reduction to coke. In case the raw oilcharging stock is a relatively heavy oil, some of its heavier componentsmay also be reduced to coke in chambers 36 and 36'. However, conditionsare so controlled in heating coil 44, as has previously been explained,that no appreciable coke deposition occurs in the heating coil.

Vapors are withdrawn from coking chamber 36 through line 48 and valve 49while vapors are withdrawn from coking chamber 36 through line 48' andvalve 49', vapors from either or both chambers passing thence throughline 50 into vaporizing chamber 8, where they commingle with theconversion products supplied to this zone from reaction chamber 5, areseparated into vaporous products and non-vaporous residual liquid andare subsequently subjected to the same treatment as that afforded thevaporous and residual liquid products from chamber 5.

The cracking coil wherein reflux condensate from the fractionator of thesystem is subjected to conversion may employ a conversion temperatureranging, for example, from 850 to 1050 F., with superatmosphericpressures ranging from 100 to 500 pounds, or thereabouts, per squareinch. A substantial superatmospheric pressure substantially equalizedwith that in the cracking coil is preferably employed in the reactionchamber although somewhat reduced pressure may be employed in this zone,when desired. The vaporizing chamber, as well as the succeedingfractionating, condensing and collecting portions of the system,preferably utilizes a substan tially reduced pressure relative to thatemployed in the reaction chamber, said reduced pressure ranging, forexample, from 100 pounds, or thereabouts, down to substantiallyatmospheric pressure. A pressure substantially equalized with or lowerthan that in the vaporizing chamber is preferred in the coking chambersalthough higher pressures up to several hundred pounds per square inch,may be employed in the coking zone, when desired, particularly when itis desirable to subject the raw oil charging stock to extensiveconversion in the coking portion of the system. The raw oil chargingstock may be heated, prior to its introduction into the coking zone, toa temperature of the order of 900 to 950 F. or more, and the pressureemployed in this heating coil may range, for example, from substantiallyatn'lilospheric to 500 pounds, or more, per square inc 7 As a specificexample of the operation of the process of the present invention, theraw oil charging stock is a 40 A. P. I. gravity Mid-Continent crudecontaining about 40% of material boiling up to 437 F. This material issubjected in the raw oil heating coil to a temperature of approximately950 F. at a superatmospheric pressure of about 350 pounds per squareinch and is introduced into direct contact with the residual oil in thecoking zone at a reduced pressure of approximately 50 pounds per squareinch. Vapors from the coking zone are supplied to the vaporizing chamberof the cracking system and reflux condensate from the succeedingfractionator of the cracking system is subjected to a temperature ofapproximately 930 F., in a cracking coil at a superatmospheric pressureof about 400 pounds per square inch. The reaction chamber is maintainedat substantially this same pressure but the pressure is reduced toapproximately 50 pounds per square inch, in the vaporizing chamber. Thisoperation may yield, per barrel of raw oil charging stock, about 70% of400 end point motor fuel having an octane number of approximately70,-about 70 pounds of coke and approximately 550 cubic feet ofuncondensable gas.

I claim as my invention:

1. A cracking process which comprises subjecting hydrocarbon oil tocracking conditions of temperature and pressure in a cracking zone, 7

continuously removing reaction products from said zone and flashdistilling the same in a flashing zone by pressure reduction, therebyforming vapors and unvaporized oil, removing the latter from theflashing zone and introducing the same to a coking zone, simultaneouslypassing additional hydrocarbon oil through a second heating zone andheating the same therein to the coking temperature of said unvaporizedoil, discharging the thus heated additional oil into the coking zone andinto contact With the unvaporized oil therein and distilling the lattersubstantially to coke by the heat of said additional oil, introducingthe vapors evolved in the coking zone into contact with the oil beingflash distilled in the flashing zone, removing the admixed vapors fromthe flashing zone and fractionating the same to condense heavierfractions thereof, supplying resultant reflux condensate to saidcracking zone and finally condensing the fractionated vapors.

2. A cracking process which comprises heating relatively cleanhydrocarbon stock, formed as hereinafter set forth, to crackingtemperature under pressure while flowing in a restricted stream througha heating zone, introducing the heated oil to a reaction zone maintainedunder cracking conditions of temperature and pressure, continuouslyremoving reaction products from the reaction zone and flash distillingthe same in a flashing zone by pressure reduction thereby forming vaporsand unvaporized oil, removing the latter from the flashing zone andintroducing the same to a coking zone, simultaneously passing additionalhydrocarbon oil through a second heating zone and heating the sametherein to the coking temperature of said unvaporized oil, dischargingthe thus heated additional oil into the coking zone and into contactwith the unvaporized oil therein and distilling the latter substantiallyto coke by the heat of said additional oil, combining vapors evolved inthe coking zone with vapors evolved in the flashing zone andfractionating the admixed vapors to condense heavier fractions thereof,supplying resultant reflux condensate to the first-mentioned heatingzone as said relatively clean stock, and finally condensing thefractionated vapors.

3. A cracking process which comprises heating relatively cleanhydrocarbon stock, formed as hereinafter set forth, to crackingtemperature under pressure while flowing in a restricted stream througha heating zone, introducing the heated oil to a reaction zone maintainedunder cracking conditions of temperature and pressure, continuouslyremoving reaction products from the reaction zone, flash distilling thesame in a flashing zone by pressure reduction, thereby forming vaporsand unvaporized oil, removing the latter from the flashing zone andintroducing the same to a coking zone, simultaneously passing additionalhydrocarbon oil through a second heating zone and heating the sametherein to the coking temperature of said unvaporized oil, dischargingthe thus heated additional oil into the coking zone and into contactwith the unvaporized oil therein and distilling the latter substantiallyto coke by the heat of said additional oil, introducing the vaporsevolved in the coking zone into contact with the oil being'flashdistilled in the flashing zone, removing the admixed vapors from theflashing zone and fractionating the same to condense heavier fractionsthereof, supplying resultant reflux condensate to the first-mentionedheating zone as said relatively clean stock, and

finally condensing the fractionated vapors.

EDWIN F. NELSON.

